I don't dare compare the importance of decentralization with other good projects, but I do regard it as something very important. Here are a few projects that I know about and find interesting.

A social network that has been around for quite a while is diaspora*. I think its future may have been unclear a while back, but as of now it's being actively developed by the community and things are looking well! I'm using in myself and I've had good experience with it.https://diasporafoundation.org/

Another social network more often compared to Twitter is GNU Social. The already mentioned Mastodon should be compatible with it, at least for now, as far as I know. I don't use it, but I would place much trust in GNU Social, since the GNU project is like the embodiment of passionate freedom.https://gnu.io/social/

One program I plan on using is GNU Ring, a secure and distributed (peer to peer) network for text, audio and video communication. I've tried using a long while back and it worked fairly well. Nowadays I can't get it to run on my installation of Parabola, but I keep an eye on it and I think it's the best thing of its kind we have now. The developers (Savoir-Faire Linux) appear to care about freedom very much, too, as demonstrated by them joining the project with GNU.https://ring.cx/

For media sharing, I would have to recommend looking at GNU MediaGoblin. It aims to be a decentralized network for sharing text, images, video, audio, 3D models and possibly more! As of now, the federation part of the program has not been completed, so there are but a few instances which can not really talk to each other. But hopefully we'll get to see a breakthrough in the coming days!http://mediagoblin.org/

I've also read about Syncthing, a program one can use to synchronize data across multiple devices. I suppose one would need to have a server or another device always online to get the best out of it, but I guess someone might find it useful even without that.https://syncthing.net/

One thing I've been interested in is distributed search engine. I know about Seeks – which appears to be unmaintained – and YaCy – which is written in Java. Fortunately I've recently found out about another such project: PeARS! It's a fairly young project that I couldn't get to work myself, and I couldn't find any simple way to find out what's new and what's being worked on, but Mozilla did entrust them with some funds, so let's hope these PeARS will come to fruition!http://pearsearch.org/

And last, but certainly not least: GNUnet! I'm not sure what exactly this is or how it works. I came to understand that it's supposed to be a distributed network similar to the internet (or maybe the World Wide Web?). To me it's a bit confusing and difficult to use, but I came to understand that many people regard it as interesting, useful or important, and that it's supposed to have some very cool features, so here it is!https://gnunet.org/

I find Syncthing to be incredible. I use it daily, multiple times a day. I depend on it to sync all my computers. I have yet to run my own server, but you dont need to. It just works! I highly recommend it.

- As long as the server does not mantain a "white-list" or a
"black-list". Many email service providers appear to have such list,
and sometimes, they even completely drop the emails sent to their
clients.

- GNU Social: Microblogging.

- Supports "hashtags" and groups.

- Character limit is decided by service provider.

- Supports attaching images. I don't know if they have a limit.

- Diaspora: Social network.

- Posts can have as many things as you wish.

- Supports attaching images. I don't know if they have a limit.

- Does not accept advanced markup (/e.g./: HTML tables).

- Interface heavy, and also has intensive use of JavaScript.

- Pump.io: Social network.

- Website: [[http://pump.io/]].

- Posts can have as many things as you wish.

- Accept advanced markup.

- Lightweight interface.

- Multiple clients.

- Image uploads are limited to some file size. I think this depends on
the server.

- You can backup your activity to a file in your computer, even the
list of people you're following.

- Doesn't support "hashtags", as far as I can see.

- Official standardization through W3C is under way, the standard is
called ActivityPub. Contrary to other social networks, this provides
ways for other sites to integrate with Pump.io service providers,
thus allowing for cool things like: games, news feed makers,
calendar and event listings, and even general event notifications
(/e.g./: arrivals, acceptance, denials).

- GNU MediaGoblin: Media publishing.

- Website: [[http://www.gnu.org/software/mediagoblin/]].

- They also plan to use ActivityPub standard.

- I also suggested them to integrate this with GNUnet.

- XMPP: Instant text message.

- I'm not sure what is the future of this.

- Has "extensions" for voice and video, but the service providers that
implement these don't have "fall backs" in case the other part
doesn't support the extensions, and these are optional.

- I don't use it.

- SIP: Phone calls.

- I'm not sure what is the future of this.

- I don't use it.

* Distributed (you're your own provider, but occasionally receive help
from others)

- GNU Ring: Instant communication.

- I prefer this over other communications.

- Needs more work, but at least the project itself decided to join
GNU, so that's awesome compared to similar projects.

- Messages to off-line people are resent three times, one per minute,
after this they are dropped. I think there are plans to increase
this time.

- Optional: Although your Ring identity is a long series of
characters, you can also share it via QR code (which is already
offered in most Ring clients), and also can register a short
username to that identity. You can always be called through the full
Ring identity, since the short username is only a shortcut. You can
also choose *not to* register a short username.

- Tox: Instant communication.

- Website: [[https://tox.chat/]].

- I'm not sure what is the future of this.

- I don't know much about it.

- BitMessage: Email-like, also supports mailing lists.

- Website: [[https://bitmessage.org/]].

- I'm still planning on using it.

- According to what I have read about it, it has low attachment file
size. For me, this is not a problem, but this depends on each person
to evaluate. :)

- Emails to off-line people are bounced between others for at least
two days, after this the message is dropped/discarded. I don't know
if it has ways to tell the sender what is the status of the message.

- GNUnet: Publish/share anything.

- I'm still planning on using it.

- Unavailable (or no-longer-shared) content is automatically removed after
some time (six months, I guess).

- The more you leave it running, the more content is made available
for you, and the more other people are made aware of the content you
already share. This doesn't mean you automatically share the
contents that are made available, it just means that more things get
"advertised" to you.

- Allows people to have changeable content, but this doesn't mean that
those already sharing the old content cannot go back to sharing it
instead. The "changeable content" option is not enabled by default.

- Twister: Microblogging.

- Website: [[http://twister.net.co/]].

- I'm still planning on using it.

- I don't know much about it.

- GNU Taler: Taxable Anonymous Libre Electronic Reserves

- Website: [[http://www.gnu.org/software/taler/]].

- I'm still planning on using it.

- I don't know if this is distributed, but appears to be so, and seems
even more awesome than Bitcoin.

- I don't know much about it.

- Allows people to do payments, with any currency (/e.g./: Brazilian
Real, US Dollar, Bitcoin), thus I consider it a better promise than
Bitcoin, also because it has goal to be taxable.

Been using Mastodon for a nearly a week now and I have to say I am loving it. Mostly I like the community is vibrant and motivated. I do think this may be the killer app of decentralized social interactions. The traction especially in Japan and France is very high. Also the timing now where all the mainstream social networking apps seem to be increasing the grip on the user, forcing ads and ramping up malefic "features". Combined with well known and factually acknowledged in the mainstream CIA backdoors/ hacking... This is it. I know its basically no different than GNU Social, but what can I say people are stupid :D We like cool mascots, especially ones that sound like an awesome metal band. ;)